Effects of subsoiling technique on water distribution and storage of the albic soil

The albic soil (profile stratification: black soil layer, albic layer, and illuvial layer) has low permeability and a compacted albic layer, which is a typical low-yielding soil with constraint factors in Heilongjiang Province. Subsoiling techniques can disturb the albic soil layer and improve water conditions in the rooting zone. In this study, we investigated the effect of two subsoiling techniques, i.e. surface soil interlayer mixing (mixing the albic layer with the illuvial layer) and subsoil interlayer mixing (mixing the black soil layer with the albic layer), on soil water distribution and storage through monitoring soil water dynamics during the maize growth period. Results showed that the albic layer of control exhibited a bulk density 23.6% higher than that of the black soil layer and an extremely low saturated hydraulic conductivity (0.0013 cm·h^-1). This impeded upward water movement during the seedling stage of maize when rainfall was scarce, resulting in the formation of dryness in top and albic layers. During the frequent rainfall period after the jointing stage, the low permeability of the albic layer caused water retained in the upper soil layers. After using the subsoiling techniques, the average saturated hydraulic conductivity for 0-60 cm soil layer reached 12.29 cm·h^-1 under surface soil interlayer mixing and 14.09 cm·h^-1 under subsoil interlayer mixing treatments, being 4.9 to 5.7 times of the control. Compared to the control, both techniques increased soil water content in the albic layer by 93.2% during the maize seedling stage. During periods of the jointing stage with frequent rainfalls (July 15 to July 19), the average soil water content in the 0-30 cm layer decreased by 10.3% and 8.3% respectively, and soil water infiltration was improved. Water storage capacity in the rooting zone (0-60 cm) increased by 5.5% during the growing season. Our results indicated that subsoiling techniques ameliorate the uneven soil water distribution within the albic soil profile during the maize growing season, with the subsoil interlayer mixing showing the better efficacy.